I plan on building on a PWF. The nature of PWF suggests it is fine with distributed loads but it’s capability to handle point loads is less obvious. My south wall will have several 6 foot wide windows. normally a header above the window concentrates the distributed load from above into point loads at the sides of the opening. I’m thinking of adding headers below the windows to “re-distribute” the loads to the foundation. I have 2 parallel 2×4 walls. In all cases the headers will be plywood box headers with 1×3 internals and 1/2′ plywood faces, insulated with 2 1/5″ mineral wool. What level of excess is the header below?